Justin Bieber canceled his upcoming appearances at the Macy's Thanksgiving Day Parade and "The Late Show with Stephen Colbert" in New York City, Billboard reported. The pop star made the announcement via Twitter along with an apology, but he did not name a specific reason for the cancellation.

"My apologies to @colbertlateshow as I won't be able to make it to nyc tomorrow for the show. I look forward to making it up to you soon," Bieber, 21, wrote on Twitter.

"@StephenAtHome thank you for the understanding as sometimes life kicks our ass and we need to deal with it. I will see u soon. Thank you," he tweeted again, this time directly at Colbert.

Bieber was scheduled to appear on Tuesday night's episode of the "Late Show" and also tape his headline performance for the Macy's Thanksgiving Day Parade on CBS. He did not disclose the reason for cancelling, but sources close to Bieber's camp say that he's dealing with "personal" issues, according to TMZ. It's speculated that Bieber's problems are not related to drugs and alcohol, but that the singer is just emotionally and mentally exhausted.

He also reportedly offered to tape his Thanksgiving Parade performance from Los Angeles, but the network refused, according to a CBS Thanksgiving Day Parade insider.

"Justin made arrangements, and then CBS decided if he's not doing Colbert, he's not doing it all," the insider told Hollywood Life. "He didn't back out, he was willing to do it from LA."

A replacement for CBS's Thanksgiving Day Parade headline slot has yet to be announced.

See Bieber's tweets below.